The present invention relates to pressure compensation valve arrangements for valve stems which are provided with valve heads biassed under spring pressure into sealing engagement against a rigid annular valve seat of a support. The valve stem passes through the valve hole and is movable therethrough by spring pressure acting against the other side of the valve support such that with the occurrence of excess or vacuum pressure the valve is opened automatically and operates to automatically ensure pressure compensation.
It has been proposed in U.S. Pat. Nos. 1,378,724 and 3,080,995 (CURTISS-WRIGHT) or German Offenlegungsschrift Nos. 1,580,140 and 2,028,383 in fuel tanks of automotive vehicles to use automatically acting valves within the closure caps of such tanks. These valves are retained tightly sealed subject to compression spring force and, with the occurrence of excess or reduced pressure in the tank, a respective valve opens automatically and again seals automatically tightly subject to spring force after pressure compensation has occurred. A serious disadvantage of such automatically acting pressure compensation valves resides in that, especially with the occurrence of large pressures during the opening of the valve, the compression springs located intermediate the valve hole and the interior of the fuel tank inadequately effect automatic opening and closing of the valve for gas pressure compensation. A more adverse effect particularly results if with the occurrence of increased pressure within the sealed fuel tank, the valves open correspondingly further against spring pressure forces which consequently produce a stronger compression of the springs. The cross-sectional flow area towards the valve hole will become forcibly constricted with the increased opening of the valve head. Eventually a fully compressed spring will block all gas flow towards the valve hole.